Avalanche Forecast

Issued: Mar 5th, 2017 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Deep Persistent Slabs.

william lawson, Parks Canada

Banff Yoho Kootenay.

Avalanche control on Mt Bosworth (March 6,2017), no backcountry recreation in this area. A reactive storm slab has produced large avalanches through the forecast region.

Summary

Weather Forecast

Light precipe with accumulation of 3-6 cm over the next 24 hours, temperatures are expected to stay cooler through tuesday with lows of -20 and highs around -10. Forecasted winds will remain lightÂ to moderate in the alpine for tomorrow.

Snowpack Summary

20-40cm of new has fallen during the storm. This has developed a storm slab that sits over a supportive mid-pack, with the lower half of the snowpack consisting of weak facets and depth hoar. New cornice growth and isolated wind effect near ridge crest developed during the storm but has now tapered off as the winds died down .

Avalanche Summary

Natural and skier triggered avalanches to size 3 were reported today, initiating in the storm slab and in some cases stepping down to the deep persistent problem. Explosive control work on the sunshine road produced several size 2-3 avalanches. A number of remote triggered storm slabs have occurred in the last 48 hours.

Confidence

Problems

Storm Slabs

20-40cm of new snow has developed a storm slab in the alpine and at tree line, failure of this layer could provide enough of a load to trigger deep persistent layers resulting in large avalanches.

The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Deep Persistent Slabs

There is a thick slab over a structurally weak snowpack in most areas. Avoid thin parts of a slope or rocky outcrops at tree line and above. We are seeing increased natural activity as a result of the new snow including remote triggering.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Be aware of thin areas that may propogate to deeper instabilites.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

2 - 3

Valid until: Mar 6th, 2017 4:00PM